The CXP boost gives a bonus pool that adds to what you earn by a specified percentage until it is exhausted. In other words, you buy it, and whether you play a lot of=r a little, it will always eventually give you exactly the amount of bonus CXP specified.

For example, if the amount is 1000 bonus CXP with a 20% boost, it means you will earn 20% bonus CXP until the amount of bonus CXP equals 1000.